Exhaust gas generated in the gasoline combustion process contains CO, HC and NOx. Three-way catalysts are known as exhaust gas purification devices that purify these three types of exhaust gas purification components. Three-way catalysts have a configuration provided with a substrate and a catalyst coating layer on the substrate in which a precious metal such as Rh, Pt or Pd is supported on a carrier particle. Among these precious metals, Rh mainly fulfills the role of reducing NOx while Pt and Pd mainly fulfill the role of oxidizing HC and CO.
In relation thereto, Patent Document 1 discloses an exhaust gas purification device having a catalyst layer on a substrate, the catalyst layer containing an alumina carrier particle supporting Pd and a ceria-zirconia carrier particle supporting Pt and/or Rh.
In Patent Document 1, as a result of supporting Pd on an alumina carrier particle having superior heat resistance, in addition to high catalytic activity being able to be maintained by inhibiting Pd particle growth, the oxygen concentration in the atmosphere can be adjusted by the ceria present in the zirconia-ceria carrier particle. As a result, it is reported that the NOx reduction reaction along with the CO and HC oxidation reactions are improved and exhaust gas purification performance can be improved.